是否可以使用 Gson.fromJson() 来获取 ArrayList<ArrayList<String>>? [英] is it possible to use Gson.fromJson() to get ArrayList&lt;ArrayList&lt;String&gt;&gt;?

问题描述

假设我有一个 json 数组

String jsonString = [["John","25"],["Peter","37"]];

我想将其解析为 ArrayList> 对象.当我使用

i would like to parst this into ArrayList<ArrayList<String>> objects. when i used

Gson.fromJson(jsonString,ArrayList>.class)

它似乎不起作用，我通过使用来解决

it doesn't seem to work and i did a work around by using

Gson.fromJson(jsonString,String[][].class)

有没有更好的方法来做到这一点?

is there a better way to do this?

推荐答案

是的，使用 TypeToken.

Yes, use a TypeToken.

ArrayList<ArrayList<String>> list = gson.fromJson(jsonString, new TypeToken<ArrayList<ArrayList<String>>>() {}.getType());

TypeToken 允许你指定你真正想要的泛型类型，这有助于 Gson 在反序列化过程中找到要使用的类型.

The TypeToken allows you to specify the generic type you actually want, which helps Gson find the types to use during deserialization.

它使用这个 gem:Class#getGenericSuperClass().它是一个匿名类的事实使它成为 TypeToken<...> 的子类.相当于一个类

It uses this gem: Class#getGenericSuperClass(). The fact that it is an anonymous class makes it a sub class of TypeToken<...>. It's equivalent to a class like

class Anonymous extends TypeToken<...>

该方法的规范指出

如果超类是参数化类型，返回的Type对象必须准确反映源代码中使用的实际类型参数.

If the superclass is a parameterized type, the Type object returned must accurately reflect the actual type parameters used in the source code.

如果您指定

new TypeToken<String>(){}.getType();

返回的 Type 对象实际上是一个 ParameterizedType，您可以在其上使用 ParameterizedType#getActualTypeArguments().

the Type object returned would actually be a ParameterizedType on which you can retrieve the actual type arguments with ParameterizedType#getActualTypeArguments().

类型参数将是上述示例中 java.lang.String 的 Type 对象.在您的示例中，它将是 ArrayList> 的相应 Type 对象.Gson 会继续沿着链条向下移动，直到构建出所需类型的完整地图.

The type argument would be the Type object for java.lang.String in the example above. In your example, it would be a corresponding Type object for ArrayList<ArrayList<String>>. Gson would keep going down the chain until it built the full map of types it needs.

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